1. Field of the Invention
The present invention relates to a scanning method, and more particularly, the present invention discloses a scanning method that reduces a number of calculations performed during calibration to save time.
2. Description of the Prior Art
Scanning devices are peripherals commonly found in home and office computing systems. Scanners are capable of determining image content of a document, and converting the image content of the document into a form that may be manipulated by a computer user through various related software packages. Practically, this manipulation may include converting image data of old documents into text data for database use, or changing image content of a scanned photograph for tabloid use.
Whatever the use, prior art scanners spend an inordinate amount of time warming up and performing self-calibration. In one aspect, calibration is performed to improve image scans by calculating, and eventually correcting for, differences in light source intensities over the length of the light source.
Please refer to FIGS. 1-3. FIG. 1 is a diagram of a prior art scanner 10. FIG. 2 is a graph of a distribution of intensity data, with an average intensity 32 demarcated. FIG. 3 is a graph showing light intensities relative to a position along a calibration paper 20 of the scanner 10, including a reference to the average intensity 32 of FIG. 2. As shown in FIG. 1, the scanner 10 also comprises a scanning module 12 for retrieving data from a document 14, a transparent plate 16, upon which the document 14 may be placed, a memory 17 for storing programs and data, and a central processing unit (CPU) 19 for processing data retrieved from the document 14. The calibration paper 20 is positioned before the document 14, relative to a direction of movement of the scanning module 12.
Please refer to FIG. 4, which is a flow chart of the prior art scanning method. Before scanning the document 14, the scanning module 12 performs a calibration scan. In the calibration scan, the scanning module 12 scans the calibration paper 20. Upon completion of the calibration scan, the CPU 19 receives data such as that shown in FIG. 2. Again, FIG. 2 shows a distribution of intensities. The CPU 19 removes upper and lower 5% of the intensity distribution data to form a range of acceptable intensities, which will also be referred to as an effective image range of the image data. Only data falling within the effective image range are used in calculating the average 32.
As shown in FIG. 3, light intensities of the light source typically vary over the width of the transparent plate 16. Therefore, the CPU 19 lifts or drops the intensity of each scanned pixel to the intensity level of the average 32.
Again, one calibration scan is performed before every scan of the document in this prior art method. Then, the CPU 19 both determines the effective image range of the image data, and calculates the average 32. This adds significant time when a user performs multiple scans, because the CPU 19 embedded in the scanner 10 is typically slow.
It is therefore an objective of the present invention to provide a scanning method that saves time.
According to the first claimed invention, the scanning method saves time by reducing processor calculations. The scanner has a housing, a transparent platform installed on the housing, a document positioned on the transparent platform, a scanning module, a calibration paper, a memory, and a processor. The scanning method starts by having the scanning module to scan the calibration paper. If no scanning pass has been performed since the scanner is turned on or if a period of time, since generating a last effective image range determined after the scanner is turned on and before scanning the calibration paper, has elapsed, define a new effective image range according to the image data of the plurality of pixels and calculate an average of image data which are within the new effective image range. If the period of time, since generating the last effective image range, has not elapsed, calculate an average of image data which are within the last effective image range. The scanning module then uses the average to calibrate an image generated by scanning the document.
According to the second claimed invention, the calibration paper is scanned to collect the image data, the effective image range is defined according to the data, and the average is calculated according to the effective image range. Then, before beginning a scanning pass, it is determined whether or not the calibration paper should be scanned. If not, the image generated by scanning the document is calibrated according to the previously calculated average.
It is an advantage of the claimed invention that number of calculations performed by the processor is greatly reduced, which saves a great amount of time in processing due to the slow speed of the processor.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.